It's down to personal preference the way you paint them Rusty. I sometimes paint the lighter colour first, with the darker colour (Dark Green) over the top, and sometimes paint them separately. In this scale, it's probably easier to paint the lighter top colour first, overall, then mask and paint the green. Obviously, paint and mask the underside first. The patterns on the Spit and Hurri were the same, to two versions, known as 'A' and 'B' Schemes, one being a mirror image of the other. Regardless of edge definition, in this scale a hard demarcation will be required.
Virtually any clear coat can be used over Humbrol enamels - I've used this paint for 50 years, and it used to be the best in the World, but since the demise of Humbrol as a company and the loss of the factory, quality has declined substantially.
Many of us here use 'Future' as a gloss coat, and I use this, mixed with Tamiya Flat Base, as a finish coat, when the proportion of Flat base can provide anything from a full matt, to a semi-gloss finish. Only small amounts of FB are needed, and this should be mixed thoroughly before use, and then tested on some painted scrap to determine the finish.
Hope this helps.